The control of the quality of a fluid in a circuit, such as a lubrication circuit for machinery, is essential in order to keep the operating parts of the machinery in proper working order.
Devices for detecting the presence of impurities in the fluid are used to maintain the quality of the fluid. Typically, the devices monitor the transparency of the fluid in order to detect any impurities. It is also known to incorporate magnets into these devices to attract metallic impurities. An electrical circuit, the conductivity of which is effected by the presence of the metallic impurities, is used to monitor the presence of the impurities and to activate an alarm or other signal when the impurities reach a predetermined level. While such devices have proved successful, the complexity of the electric circuits utilized raise the cost of the devices and reduce their reliability.